The proposed research will explore the chemosensory properties of the notable occupational and environmental contaminants formaldehyde, acrolein, and phenol. Properties of interest include odor and irritation of the nose and throat. Initial psychophysical experiments will map the absolute sensitivity to and the perceived intensity of these agents in a group of 100 persons. The group will be chosen in such a way as to analyze how gender, smoking status, age, and prior occupational exposure to formaldehyde may influence sensory impact. Differences that emerge from psychophysical testing will receive further attention in measurements of reaction time and of a reflex transitory apnea that may provide an objective appraisal of chemosensory status. Subsequent experimental work will include exposures up to 3 hrs in a unique, aluminum-lined environmental chamber that can accommodate groups of participants under realistic conditions of exposure. Experiments in the chamber will focus on the time-course of sensations aroused by the contaminants and will allow a direct comparison of the sensations of occupants exposed continuously with those of visitors exposed only every few minutes. These experiments will be performed on a series of successive days in order to capture any day-to-day sensitization. Such sensitization may occur in persons unaccustomed to exposure. Persons previously exposed occupationally may exhibit generally lower sensitivity to all chemosensory stimuli. Since short-term exposure, as well as long-term exposure, to the short-chain aldehydes has been implicated in olfactory anesthesia, some of the proposed experiments will explore the sensitivity of students exposed for 3-4 hours at a time in anatomy laboratories. Experiments on the perceived intensity of gas-phase mixtures of formaldehyde and other stimuli should also settle the long-discussed issue of whether formaldehyde causes an immediate anesthetic effect on olfaction. The results will address issues of direct public health concern. They may confirm adverse chemosensory consequences of occupational exposure to aldehydes and they should clarify the hitherto poorly specified quantitative sensory properties of these agents.